创建具有特殊条件的sql str [英] create sql str with special condition

问题描述

创建具有特殊条件的sql str

hellow

我有2个表

表a（代码，价格，支票）

表b（代码，百分比）

我想在下面创建一个sql字符串：

create sql str with special condition
hellow
I have 2 table
Table a(code, price, check)
Table b(code, percent)
I want to create a sql string such below:

Select a.code, a.price, (price * percent) as new_field
From a,b 
Where a.code = b.code

这个条件必须在sql str中考虑：

And this condition must be consider in sql str:

If (check = 1)
{
 New_field = price * percent
}
Else
{
 New_field = price * percent * 8
}

现在如何将上述条件放在sql str中？

非常感谢



已添加代码块[/ Edit]

Now how can put above condition in sql str?
Thanks very much

Code block added[/Edit]

推荐答案

您应该搜索 CASE 语句。这基本上是你需要处理你的请求中的条件。



但你的查询有问题：你在表a和b之间进行连接，但是你不要在SELECT部分​​使用表b。此外，如果您使用的是MS SQL Server，则语法不正确。它应该是：

You should search for CASE statement on MSDN. This is basically what you need to handle conditions in your requests.

But there is something wrong in your query : you make a join between tables a and b, but you don''t use table b in your SELECT part. Moreover, if you are using MS SQL Server, the syntax is incorrect. It should be:

SELECT
   a.code
  ,a.price
  ,CASE
     WHEN (a.check = 1) THEN (a.price * b.percent)
     ELSE (a.price * b.percent * 8)
   END
   AS new_field
FROM a INNER JOIN b ON a.code = b.code

包含CASE声明的更改

[Edit2]用英语替换MSDN链接

Included change with CASE statement
Replaced MSDN link with an english one

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